Atlas-Able Semi-Scale Mid-Power

[Charles_McG]

3.1415926535897932384626433

I want to see you cut and measure to 26 significant figures.

 

[lakeroadster]

I want to see you cut and measure to 26 significant figures.

If I would have just put 3.14... some smart ass would have posted the 26 figures... so I figured I'd post the 26 figures, and then some... well.... nevermind.... have a great day. lol

 

[Charles_McG]

If I would have just put 3.14... some smart ass would have posted the 26 figures... so I figured I'd post the 26 figures, and then some... well.... nevermind.... have a great day. lol

Smart asses are as unavoidable as entropy and inescapable as black holes.

 

[Raptor 2]

3.1415926535897932384626433

Accuracy is paramount in rocketry!!

 

[Ez2cDave]

I don’t like to appear dumb but.....here goes. How can this rocket be stable with no fins? And what does the long narrow triangle at the back end of the rocket in the OR drawing mean?

"Blowgun Darts" are also stable, with no fins . . . "Base Drag", same principle on a fin-less rocket.

Dave F.

 

[Raptor 2]

I don’t like to appear dumb but.....here goes. How can this rocket be stable with no fins? And what does the long narrow triangle at the back end of the rocket in the OR drawing mean?

Thanks for the enlightenment provided on my questions. I’ve learnt something new. Now before this thread gets highjacked...... back to the Atlas-able to see if it really has enough base drag to be stable.

 

[Raythain]

Accuracy is paramount in rocketry!!

It is, after all, rocket science.

 

[Ez2cDave]

Thanks for the enlightenment provided on my questions. I’ve learnt something new. Now before this thread gets highjacked...... back to the Atlas-able to see if it really has enough base drag to be stable.

It might be possible to incorporate a "Drag Plate", on the base of the Atlas-Able, to increase Base Drag if the available configuration does not provide a "sufficient amount" ( whatever that value is ).

That is not in my "bag of tricks", as I have never had a need to increase Base Drag, personally.

Dave F.

 

[Daddyisabar]

When you are so desperate as to reach into a "bag of tricks" to compensate for your extremely odd and thus poor rocket design, it is a sure sign that you need to go home and re-think your life. This is what a Jedi Master said to me at the bar after a launch, waiving his hand after I inquired as to the use of powered Tungsten for maximum nose weight in a small and oddly shaped nose cone on a Dornier 217 night fighter.

Nothing but oddroc scum hanging around with base drag hacks. You will never find a more wretched hive of scum and villainy. We must be cautious. 3-4FNC is the way. Search your feelings and do not give into the Dark Side.

 

[BABAR]

3.1415926535897932384626433

More than good enough for government work!

 

[Ez2cDave]

 

[Ez2cDave]

I want to see you cut and measure to 26 significant figures.

If I would have just put 3.14... some smart ass would have posted the 26 figures... so I figured I'd post the 26 figures, and then some... well.... nevermind.... have a great day. lol

If I am not using a calculator with a Pi key, I use either 3.1416 or 3.1415926, depending on the material being scaled.

Dave F.

 

[neil_w]

I want to see you cut and measure to 26 significant figures.

No problem.

 

[Charles_McG]

Measure it with a micrometer.
Mark it in chalk.
Cut it with an axe.

 

[Ez2cDave]

Measure it with a micrometer.
Mark it in chalk.
Cut it with an axe.

Charles,

One more thing . . . Sand it with a Cheese Grater !

LOL !

Dave F.

 

[lakeroadster]

 

[jqavins]

Thick skull here.....PI x Diameter........PI is?
Never mind got it PI is Pi 3.1415.......

In other words, length is the same as the base circumference.

At 14 mph I doubt base drag hack is gonna hack it, not sure if the biggest fins in the world would help.

I don't see where I'd gain anything by using composite motors.

Consider those quotes together. Composite motors might give you the speed you need to make whatever stabilization method you choose work.

If I would have just put 3.14... some smart ass would have posted the 26 figures...

And for once in this lifetime, I would not have been that smartass. But I would add that the old 22/7 is surprisingly close, only 0.04% off, or four digits accuracy. And 355/113 is merely 85 parts per trillion. An easy to remember six digits get's you seven digits of accuracy. (Take 113355, split it in the middle to 113 and 355, then put the bigger one on top.)

 

[lakeroadster]

Composite motors might give you the speed you need to make whatever stabilization method you choose work.

I design around any design that involves clustering and composite motors.​

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I know from using them that it takes them awhile to ignite, and that "awhile" is not consistent.​

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Using 24mm BP motor clusters, fired via E-matches, has been flawless for me, thus far.​

 

[jqavins]

Oh, I get that. So I wonder how else to get that speed up. 29 mm BP motors?

E16 and F15, with D12 for reference.

 

[lakeroadster]

Oh, I get that. So I wonder how else to get that speed up. 29 mm BP motors?

E16 and F15, with D12 for reference.
View attachment 642613

Speed Up... based on what? Anything over 30 mph "Off The Rod" is acceptable, typically.​

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I design for 30 mph using the simulation, then look at the Excel file and shoot for around 5-8 degree Angle of Attack within the first few feet off the rod. This one looks pretty good.​

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[jqavins]

The possible issue is the 14 mile per hour speed at staging. @BABAR raised a concern (a year ago) that at that speed the base drag may not help enough, since all drag is very low at such a small speed. Fins don't work at such a low speed either, which is the main reason for needing a minimum speed off the rod (not that you're using fins here). It's that staging speed that @Tobor was trying to address with his suggestion of composite motors. This is all I was trying to address in response to your response to him asking why composites. He suggested composites in order to get the speed at staging up.

And then, since BABAR may have a point, and you certainly have a good point about simultaneous ignition with composites, I wonder what else could be done to get the speed at staging up. Such as the higher thrust, 29 mm BP motors.

 

[BABAR]

If I am not using a calculator with a Pi key, I use either 3.1416 or 3.1415926, depending on the material being scaled.

Dave F.

delete

 

[lr64]

Perhaps one could use special, very enthusiastic, fast igniters for clustered composite motors. I'm imagining MMX motors stuffed up the nozzles, upside down. ;-)

 

[BABAR]

Accuracy is paramount in rocketry!!

I dunno, I’ve heard nuclear weapons are kinda like a game of horse shoes. Close enough is often adequate.

 

[lr64]

This morning, when I went to brush my teeth, and I had an epiphany.... lol

View attachment 574549 View attachment 574551

If you haven't started building yet, I may have a dead one of those around to donate to the cause.

 

[lakeroadster]

The possible issue is the 14 mile per hour speed at staging. @BABAR raised a concern (a year ago) that at that speed the base drag may not help enough, since all drag is very low at such a small speed. Fins don't work at such a low speed either, which is the main reason for needing a minimum speed off the rod (not that you're using fins here). It's that staging speed that @Tobor was trying to address with his suggestion of composite motors. This is all I was trying to address in response to your response to him asking why composites. He suggested composites in order to get the speed at staging up.

And then, since BABAR may have a point, and you certainly have a good point about simultaneous ignition with composites, I wonder what else could be done to get the speed at staging up. Such as the higher thrust, 29 mm BP motors.

My bad, sorry. I pulled up the Open Rocket simulation and re-ran the numbers..​

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The rocket is traveling at 136 mph when the D12's burn out.​

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Then the E12 burns out at 127 mph​

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[jqavins]

Well, in that case, never mind.